Article Do You Use It? How TidBITS Readers Install macOS Updates - TidBITS says that “Some people even wait until Apple announces or even releases the next macOS version, under the theory that it somehow isn’t fully baked until then.”. I wait until the next major release, but not under that theory. It used to be one reason to wait was that macOS updates have become so time consuming that I’d wait until there were just the faster security updates left. But now with the sealed system volume even ...
The bash that comes with macOS is a fork of the last version distributed under version 2 of the GPL, most likely because Apple doesn’t want to distribute GPLv3 code as part of macOS, and it is ancient. They keep it updated with security fixes but nothing else, so it has gradually become less and less compatible with current bash.
Since zsh has become a popular bash replacement and it isn’t GPLv3, they switched the default shell to that.
Thanks for the insight!